Method of and damper apparatus for cleaning tube banks



Aug. 23, 1955 R. H. EVANS E 2,716,021

METHOD 0F AND DAMPER APPARATUS FOR CLEANING TUBE BANKS Filed Dec. 22, 1952 I 6 Sheets-Sheet 1 TILC'IJL.

INVENTORS RIC/ 4P0 EV/INS SIDNEY El/INS ATTORNEY Aug. 23, 1955 R. H. EVANS T AL 6 Sheets-Sheet 3 Filed Dec.

A h E n u 3 m a Y mm mi im] I:

ATTO R N EY Aug. 23, 1955 R. H. EVANS ET AL METHOD OF AND DAMPER APPARATUS FOR CLEANING TUBE BANKS 6 Sheets-Sheet 4 Filed Dec.

INVENTOR Q/Cf/AIRD H. EKG/VS O'LW ATTORNEY Aug. 23, 1955 R. H. EVANS ET AL METHOD OF AND DAMPER APPARATUS FOR CLEANING TUBE BANKS 6 Sheets-Sheet 5 Filed Dec. 22, 19 52 INVENTORS Q/c/MRD H- e'nolvs q SIDNEY v. EVflA/S ATTORNEY Aug. 23, 1955 R. H. EVANS ET AL 2,716, 21

METHOD OF AND DAMPER APPARATUS FOR CLEANING TUBE BANKS Filed Dec. 22, 1952 6 SheeiSSheet 6 INVENTORS R/cHAR/J H. EVA/V5? OI/61M.-

,4 TTOR'NE Y United States Patent 0 METHOD 0F AND DAMPER APPARATUS FOR CLEANING TUBE BANKS Richard Henry Evans, Snrbiton, and Sidney John Evans, Staines, England, assignors to The Eahcock & Wilcox fompany, New York, N. Y., a corporation of New ersey Application December 22, 1952, Serial No. 327,334

14 Claims. (Cl. 257-1) This invention relates to tubular fluid heat exchangers and, more particularly, to a novel method of and novel damper apparatus for effecting cleaning of deposited solids from the external tube surfaces of such heat exchangers by effecting a controlled flow of heating gases thereacross.

In a typical tubular heat exchanger, heat transfer from a heating fluid to a second fluid to be heated is effected by heating gases flowing over the external surfaces of tubes containing the fluid to be heated. When a bank of these tubes is arranged transversely of a gas pass, as

in an air heater, the heating gases flow transversely over the external tube surfaces. These heating gases carry non-combustible solids in suspension and, as the gases flow over the external tube surfaces, such solids tend to deposit on the surfaces. This is particularly true where the tubes of the bank extend horizontally, or at an inclination to the horizontal, across a vertical gas pass having either an upward or a downward flow of heating gases therethrough. In such case, the solids tend to deposit on the upper surfaces of the tubes.

The deposits are particularly troublesome when the tubes of adjacent rows are aligned in a vertical direction, and if the deposits are not removed they may actually bridge the spaces between the vertically aligned tubes, thus substantially blocking gas flow through these spaces. In any event, the deposits reduce the efficiency of heat transfer from the heating gases to the fluid within the tubes.

The present invention is directed to a novel method of periodically cleaning such deposits from the tube surface. In accordance with the invention, the heating gases or gaseous products of combustion flowing within the tube bank are periodically caused to flow at right angles to their normal direction of flow, or in a direction transversely of the gas pass. is effected alternately in reverse directions transversely of the gas pass within the tube bank.

To accomplish this flow control, each tube bank is provided with upper and lower sets of multiple dampers. Each set of dampers includes three dampers, such as a central damper and two end dampers each adjacent a side wall of the gas pass. The central damper is of quite considerably greater length than each of the two end dampers. Operating means are provided for the dampers whereby the latter may be selectively operated to a normally open position for unrestricted flow of the heating gases transversely of the tube bank and longitudinally of the gas pass.

When cleaning of the tube surfaces is to be effected, the operating means are so positioned as to close the central damper and one end damper on the gas inlet side of the tube bank, and the central damper and the opposite end damper on the gas outlet side of the tube bank. Thereby, the heating gases enter the tube bank adjacent one side wall of the gas pass, are confined to flow transversely of the gas pass Within the tube bank, and flow out of the tube bank adjacent the opposite Such transverse flow ice wall of the gas pass, the flow direction thus being perpendicular to the normal flow direction. After a predetermined interval, the initially open inlet damper is closed and the initially closed end inlet damper is opened. Similarly, the initially open outlet damper is closed and the initially closed end outlet damper is opened. Thus, the flow of heating gases within the heat exchanger is reversed in direction transversely of the gas pass.

Normally, the pitch of the tubes in the tube bank is less in a vertical direction than in a horizontal direction. Due to this fact, when the gases are directed to flow transversely of the gas pass within the tube bank, the flow velocity is substantially increased due to the reduced flow area subjected to the same pressure diflerential. Thus, the cleaning operation is made more effective.

The particular dampers are also a feature of the present invention. Each of the dampers comprises a series of elements, preferably tubular, extending parallel to the heat exchanegr tubes and in lateral alternation therewith. Each element has a width greater than the intertube lateral spacing, or, if tubular, a diameter equal to that of the heat exchanger tubes. These elements are normally held spaced from the adjacent row of tubes so as to permit gas flow over the tubes. To close the damper, the elements are lowered into bridging or interfitting relation, each with a pair of adjacent tubes.

For an understanding of the invention principles, reference is made to the following description of a typical embodiment thereof as illustrated in the accompanying drawings. In the drawings:

Fig. l is a diagrammatic sectional side view of a tubular air heater, associated with a vapour generating and superheating unit (not shown), and comprising four vertically spaced tube banks;

Figs. 2a and 2b are diagrammatic sectional side views of the uppermost tube bank shown in Fig. 1 but drawn to a larger scale than in that figure and illustrating gas flows effected by damper means;

Fig. 3 is a sectional side view showing the lower part of the tube bank indicated in Fig. 2b but drawn to a much larger scale than in that figure;

Fig. 4 is a sectional plan view taken on the line 4-4 of Fig. 3 but with parts of the tubes in the lower row of the tube bank omitted;

Fig. 5 is a sectional side view taken on the line 5-5 of Fig. 3 and in the direction indicated by the arrows;

Fig. 6 is a side view taken on the line 6-6 of Fig. 3 and showing one form of locking means for holding dampers shown in Figs. 3 and 4 in desired position; and

Fig. 7 is a sectional view taken on the line 7-7 of Fig. 6 and in the direction indicated by the arrows; certain background details beyond the section plane being omitted.

While the principles of invention are applicable to any tubular heat exchanger extending transversely of a gas pass, the invention is particularly applicable to a tubular heat exchanger having tubes extending horizontally, or at an inclination to the horizontal, transversely of a vertically extending gas pass. Hence, the following description is directed to such a particular embodiment of the invention.

Referring first to Fig. l of the drawings, an air heater 10 associated with a vapour generating and superheating unit (not shown), comprises four vertically spaced tube banks, 20a, 20b, Ziic and 20d, disposed with their tubes extending horizontally in a downflow gas pass 11, the upper end 8 of which is arranged to receive hot products of combustion from the unit and the lower end 9 of which is connected by a laterally extending conduit 21 to a chimney stack (not shown). The lower end 9 of the gas pass is provided with a hopper shaped bottom 29 for the collection of dust separated from the products of comtube banks 20a, 20b, 20c and 20d, each tube bank is provided with damper means adapted to'close the normal gas inlet to the tube bank except at one sideor the other side of the bank and the normal gas outlet from the tube bank except at that side of the bank at which the gas inlet is closed. To this end, as is indicated in Figs. 2a and 2b, which show the uppermost tube bank 280, two sets of dampers 12, 13 are disposed respectively above and below the tube bank, the upper set including a central damper 12b and left-hand and right-hand dampers 12a, 12c respectively adjacent the left-hand and the right-hand sides 14, of .the gas pass '11 as seen in Fig. 1, while the lower set similarly includes a central damper 13b and left-hand and right-hand dampers 13a and 13c respectively In Fig. 2a, dampers 12b, 12c, 13a, and 1312 are shown as closed and dampers 120, 13c are shown as open, while in Fig. 2b, dampers 12a, 12b, 13b, and 13c are shown as closed and dampers lZc, and 13a are shown as open.

In each of the tube banks a, 29b, 20c and 20d, the tubes are arranged in rows both horizontally and vertically, as shown in Fig. 3, the tube bank extending across the full width of the gas pass 11 from the wall 14 to the wall 15. It will be seen also from this figure that the pitch of the tubes in the bank is less in a vertical direction than in a horizontal direction.

' During service, all the sets of dampers, at both the inlets and the outlets of each bank, are normally open. When it is desired to clean the air heater, the tube banks are cleaned in sequence, starting from the uppermost bank. The procedure for, each bank is the same; for example, if thetube banklfia is to be cleaned, the central dampers 12b, 13b respectively above and below the tube bank 20a (see Figs. 2a., 2b) are closed and the upper and lower. side dampers 12c, 13a adjacent opposite sides of the tube bank are also closed, with the result that the gases'are forced to flow laterally in the tube bank through spaces between vertically aligned tubes as indicated by the arrows in Fig. 211. Since the bank has a vertical depth less than its width and the pitch of tubes in the bank is less in a vertical direction than in a horizontaldirection, the gases are forced to flow laterally through the tube bank at increased velocity, whereby the cleaning action is enhanced. The initially closed dampers 120, 13a adjacent the sides of the tube bank are then opened and the initially open dampers 12a, 13c adjacent the sides of the tube bank are closed with the result that the gases are caused to flow laterally within the tube bank in the reverse sense as indicated by the arrows in Fig. 2b; In this way the whole tube bank including corner regions thereof is effectively cleaned.

All the dampers associated with this tube bank 20a are now opened, and the procedure repeated with the subjacent tube bank, until all the banks have been cleaned.

The opposite ends of the tubes are expanded into tube plates 16 and 17 respectively, and during operation of the air heater, air to be heated is caused to flow through the interiors of the tubes from the space beyond one tube plate to the space beyond the other tube plate.

The preferred form of damper means used at both inlet and outlet of each tube bank is illustrated in Figs. 3 to 5, which show the lower (or outlet) end of the uppermost tube bank 26a with the dampers in the positions indicated in Fig. 2b. The damper means provided at the lower end of tube bank 20:: comprises a set ofthree dampers, 13a,

13b and 13c, each damper including a number of movable tubular. elements 18 arranged to extend parallel to the tubes in the lowermost horizontal row 19 of tubes in the bank andrespectively arranged in alignment with the spaces between adjacent vertical rows of tubes in the bank. The elements 18, which are of an outside diameter equal to that of the tubes of the tube bank, are adapted to be moved vertically from the open position of damper 13a removable.

as shown in Fig. 3 to the closed position of damper 13b as shown in Fig. 3 in which the elements 18 close the spaces between adjacent tubes in the lowermost row 19 of the tube bank.

Each element is located by two fingers 22 respectively extending into opposite ends thereof and each formed by a length of rod welded at its outward end to an arcuate reinforcing pad 23 itself secured by welding to a sleeve such as 24a, 24b or 24c. Each of the dampers 13a, 13b and 130 has associated with it two such sleeves, one adjacent each of the tube'plates 16, 17 of the air heater; thus dampers 13a, 13b and 13c are respectively associated with axially aligned sleeves 24a, 24b and 240 located adjacent the tube plate 17 and extending transversely of .the tubes of the tube bank a short distance below the lowermost horizontal row 19. The sleeves 24a, 24b, and 240 and three similar sleeves 24a,-24b', 240 located adjacent the tubeplate 16 are rotatably mounted in bearings 25 supported by tubes in the lowermost row of the tube bank. Each bearing (see Fig. 5) comprises two blocks 26a, 26b formed with semi-circular recesses for engagement with the periphery of the associated sleeve, block 260 being welded to a tube in the lowermost row 19 of the tube bank and the block 26b being readily To this end bolts 27 are welded to the respective sides of the block 26a and extend through tubes 28 weided to the respective sides of the block 26b,

The three sleeves 24a, 24b and 24c may be rotated independently of one another from a point outside the gas pass 11 by three tubular concentric operating shafts 30, 31 and 32. The outer operating shaft, 30, is formed by an extension of the sleeve 240, the extension being provided with a journal bearing in a plate 34 secured by nuts and bolts 35 to a girder 36 of the structural streel work associated with the air heater. A sealing plate 37, pressed by a helical spring 38 against; a housing 39 surrounding the shaft 39 and secured to the wall 14 of the gas pass, inhibits the leakage of air or gases about the shaft. The intermediate operating shaft, 31, extends outwardly and inwardly to points beyond the ends of the outer shaft 30 and is secured at its inner end to the sleeve 24b by a stud 40 extending through the wall of sleeve 24b, through a collar 41 interposed between the sleeve 24b and the shaft 31, and screw-threaded into a hole in the wall of shaft 31. The inner operating shaft 32 extends outwardly and inwardly to points beyond the ends of the intermediate shaft 31 and is secured at its inner end to the sleeve 240 in the same manner that shaft 31 is secured to sleeve 24b. Operating levers 46a, 46b and 46c are removably secured to the outer ends of the operating shafts 30, 31 and 32 respectively by clamp bolts 48.

By suitable operation of the operating levers 46a, 46b and 460, and of corresponding operating levers 46a, 46b and 460' associated with the opposite ends of the tubular elements 18 forming the dampers 13a, 13b and 130, the group of tubular elements comprising a damper may be adjusted to a closed position, i. e. that of the dampers 13b, 13c in Fig. 3, in which the tubular ele ments 18 respectively serve to block substantially completely the spaces between adjacent tubes in the lower row 19 of the tube bank, or to an open position, i. e. that of the damper 13a in Fig. 3, in which the tubular elements are spaced from the adjacent tubes of the tube bank. It will be seen that the tubular. elements 18. are supported by the fingers 22 both when the dampers are in the open position and when they are in the closed position.

The set of dampers associated with the upper or inlet end of a tube bank are substantially similar to the set of dampers described above, but the tubular elements 18 are lowered to close the spaces betwen'adjacenttubes in the uppermost row of tubes in the tube bank and'are raised to an open position. In the case of the set of dampers associated with the upper or inlet end of the tube bank, when a damper is in the closed position, the.

tubular elements 18 concerned respectively rest .on pairs of tubes of the tube bank, but when the damper is in .its .open position, the tubular elements are supported by the fingers 22.

A suitable holdingarrangement for the three operating levers 46a, 46b, 460 is shown in Figs. 6 and 7 in which .a shaft 50 suitably mounted in the structural steelwork associated with the air heater, pivotally supports three locking bars 56a, 56b and 56c, respectively associated with the operating levers 46a, 46b and 46c, each of the i locking bars consisting of two side plates '57 and 58, held in spaced relationship by short spacing sleeves 59 mounted on the shaft 50 and, at a point remote from theshaft, by a nut and bolt 69 and a spacing washer 61. The three locking bars are held in spaced relationship with one another along the shaft by long spacing sleeves 62 fitted on the shaft 50. Each operating lever 46a, 46b and 460 is provided at a point adjacent its outer end with a locking pin .63 extending on both sides of the lever and of such a diameter as to fit within notches 64 formed in the lower edge of the locking bar, which bar is so arranged relative to the operating lever that the lever extends freely between the two plates 57 and 58 on the same side of the shaft 50 as the nut and bolt 60. The

ends 68a, 68b and 63c of the three locking bars 56a, 56b

and 56c remote from the nuts and bolts 60 are respectively biassed by springs 69a, 69b and 69c in such a direction that the pins 63 are held in place within the notches 64. By these means, the operating levers may be main- :tained in any one of a number of desired operating positions. To facilitate adjustment of the operating levers, 46a, 46b, 460, a separate operating handle 75 is provided, which is formed with a socket 76 which may be pushed onto the end of any one of the operating levers, and which is shown in Figs. 6 and 7 as being placed in operating position on the operating lever 460, the dampers 13a, 13b, 130 being in the positions indicated in Fig. 2a. Pivotally mounted on a pin 77 welded to the socket 76 is a bell crank lever 78 one arm 79 of which extends outwardly adjacent the operating handle 75 and the second arm 80 of which is of forked construction having two forks 81 and 82 extending one on either side of the socket 76 and carrying at its end a pivoted roller 83. A spring 84 attached at its opposite ends to the arm 80 adjacent to the roller 83 and to the socket 76 respectively biasses the arm 80 of the bell crank lever away from the adjacent locking bar. To disengage the locking bar from the locking pin 63, the arm 79 of the bell crank lever 78 is pulled towards the operating handle 75 against the force of the biassing spring 84 and the roller 83 causes the locking bar concerned to rotate on the shaft 50 against the force of the spring 690, and once the pin 63 is clear of the notch in the locking bar, the operating lever may be moved to a desired new position; upon release of the bell crank lever 78, the spring 69c is permitted to rotate the locking bar in order that the pin 63 may enter into the appropriate notch 64 on the locking bar, so that the damper operating lever is locked in the desired new operating position. The operating handle 75 may now be removed from the operating lever.

A similar holding arrangement is provided for the three operating levers 46a, 46b and 460.

By the use of the preferred form of damper means described above, in which the tubes of the lowermost (or uppermost) row of the air heater bank form, in elfect, part of the damper surface when the damper is closed, the area of the damper proper which is subject to gas pressure is materially reduced, so reducing the total force acting on the damper. As a result, both the damper and the operating means therefor may be of lighter construction, the damper is easier to support and actuation of the damper is facilitated.

While a specific'embodiment of the invention has been shown and described in detail to illustrate the application of the invention principles, it will be understood that the invention may .be embodied otherwise without departing from such principles.

What is claimed is:

1 l. A method of cleaning the external tube surfaces .of a bank of heat exchanger tubes extending transversely ofa gas pass and contacted by heating gases flowing along the gas pass and across the tubes, the heating gases .carrying non-combustible solids in suspension which solids tend to deposit on the gas-contacted external surfaces of ithe tubes; such method comprising periodically re-direot ing the heating gases to flow transversely across the tubes within the tube bank alternately in reverse directions transversely of the gas pass.

"2. A method of cleaning the external .tube surfaces of a bank of heat exchanger tubes extending transversely of agas pass and contacted by heating gases flowing along the gas pass and across the tubes, the heating gases carrying non-combustible solids in suspension which solids tend to deposit on the gas-contacted external surfaces .of the tubes; such method comprising periodically re-directing the :heating gases to fiow transversely across the tubes within the tube bank alternately in reverse directions transversely of the gas pass and at a substantially increased =velocity.

3. In combination with a bank of heat exchanger tubes extending transversely of a gas pass and contacted by heating gases "flowing along the gas pass and across the tubes, the heating gases carrying non-combustible solids in suspension which solids tend to deposit on the gascontacted external surfaces of the tubes, an arrangement for cleaning such deposits from the external tube surfaces-comprising damper means normally operable to provide for flow of the heating gases transversely of the entire lateral extent of the tube bank and longitudinally of the gas pass; and means selectively operable to position said damper means to close the normal gas inlet to the tube bank except adjacent one side of the gas pass and to close the normal gas outlet from the tube bank except adjacent the opposite side of the gas pass at which the normal gas inlet to the tube bank is closed, or to close the normal gas inlet to the tube bank except adjacent such opposite side of the gas pass and to close the normal gas outlet from the tube bank except adjacent such one side, to direct the heating gases transversely of the tubes within the tube bank and alternately in reverse directions transversely of the gas pass.

4. The combination claimed in claim 3 in which said damper means comprises a first set of dampers extending across the gas inlet of the tube bank and a second set of dampers extending across the gas outlet of the tube bank, each set including a pair of end dampers each adjacent a side of the gas pass and a central damper of considerably greater length than either end damper.

5. The combination claimed in claim 3 in which the pitch of the tubes along the gas pass is less than the pitch of the tubes transversely of the gas pass, whereby the velocity of the heating gases is substantially increased when flowing transversely of the gas pass.

6. The combination claimed in claim 3 in which said damper means comprises a first set of dampers extending across the gas inlet of the tube bank and a second set of dampers extending across the gas outlet of the tube bank, each damper comprising a series of tubular elements extending parallel to the heat exchanger tubes in alternation therewith transversely of the gas pass, the tubular elements having diameters substantially equal to the tube diameters; said operating means being operable to selectively position each set of tubular elements to close the spaces between the tubes of the inlet and outlet rows of tubes of the heat exchanger.

7. Damper means for controlling fluid flow transversely of tubes of a tube bank comprising, in combination, a series of elements extending parallel to the tubes and in lateral alternation therewith, each element having a width greater than the inter-tube lateral spacing; and means selectively operable to position said elements to close the inter-tube lateral spaces. r

8. Damper means as claimed in claim 7 wherein the elements, when in the damper closed position, respectively engage pairs of tubes of the tube bank.

9. Damper means for controlling fluid flow transversely of tubes of a tube bank comprising, in combination, a series of tubular elements extending parallel to the tubes tubes in alternation therewith, the tubular elements having diameters substantially equal to the tube diameters; and

'means selectively operable to position said elements to close the inter-tube lateral spaces.

10. Damper means as claimed in claim 9 wherein the 1 elements, when in the damper closed position, respectively engage pairs of tubes of the tube bank.

11. Damper means for controlling fluid flow transversely of tubes of a tube bank comprising, in combination, "a series of tubular elements extending parallel to the tubes in alternation therewith, the tubular elements having diameters substantially equal to the tube diameters; operating members each extending perpendicularly to said elements along opposite ends thereof, each member 'having a plurality of longitudinally spaced fingers projecting therefrom and each finger engaging in an end of a tubular element; and means operable to selectively operate said members to move said fingers to position said elements to close the inter-tube lateral spaces.

l2. Damper, means for controlling fluid flow transversely of tubes of a tube bank comprising, in combination, a series of tubular elements extending parallel to the tubes in alternation therewith, the tubular elements having diameters substantially equalto the tube diameters operating shafts each extending perpendicularly to said elements along opposite ends thereof, each shaft having a plurality of longitudinally spaced fingers projecting therefrom and each finger engaging in an end of a tubular element; and means operable to selectively rock said shafts to position said elements to close the inter-tube lateral tubular element; and means operable to selectively rock said shafts to position said' elements to close the intertube lateral spaces.

l4. Damper means as claimed in claim 13 wherein the elements are arranged in sets each constituting an individ: ual damper; and the operating shafts each include a series of concentric telescoped shafts each operatively associated with the elements of a different individual damper.

References Cited in the file of this patent FOREIGN PATENTS 7 532,557 7 France Nov. 17, 1921 621,876 Germany Nov. 14, 1935 

